I have 3..the little Harbor Freight model, the Delta and one I bought a frame for and bought a motor seperatly.
The Delta is pretty good for all kinds of stuff, and has a side disc sander, really useful. The Harbor freight sander is ok, but not as good. I use the Delta way more.
The one I put together, I made pretty much for making (predator call) toneboards. I installed a 1750 rpm motor on it. WAY better than the 3450 or so little motors on the other two, they are just way to fast. You have more control and get a better finish on stuff with the slower motor. And be aware a belt sander, even a small one can ruin stuff in a hurry, especially something like a toneboard. And like stated above, will eat up a hardened jig.
Its a 1x42 belt size, and you can get all kinds of grits in that size belt. I use
www.truegrit.com. I bought the frame at Lee Tools and the motor from Grainger and a light switch from Lowes. Very easy to build. Small but handy sander.
I use it to sharpen tools as well, with a 320 grit J weight belt. Very effective.
Also, the platen is thicker than the other two, more solid and less flex, and really helps out.
Not a very good pic of it, but happened to have it handy..
Mark